🚀 How Zoom Calls Help Us Understand Computer Networking

Zoom & The Internet

Have you ever joined a Zoom call and wondered how your voice and video reach someone miles away almost instantly? Behind the scenes, a complex web of networking technologies works together to make this magic happen. Let’s break it down in a fun and simple way!

Zoom relies on the internet to transmit audio, video, and messages in real time. When you join a meeting, your device connects to Zoom’s servers using the internet, where data is broken into small packets and sent through various network layers. These packets travel across routers, cables, and wireless signals to reach other participants almost instantly. Technologies like DNS, TCP/UDP, and TLS encryption ensure a smooth, secure, and fast communication experience, making virtual meetings feel seamless.

🤔 Feeling Lost in Tech Terms? You’re Not Alone!

If terms like HTTP, TCP/UDP, and DNS make your head spin, don’t worry! By the end of this blog, these concepts will be crystal clear. Let’s start by understanding how the Internet itself works!

🌐 How the Internet Works (A Simple Explanation)

The internet is like a giant postal system that delivers digital messages instead of letters. When you send a message or start a Zoom call, your data travels in small packets across networks to reach its destination. Here’s how:

📌 1. HTTP – The Language of the Web

Hypertext Transfer Protocol (HTTP) is how web browsers and apps communicate with servers to fetch web pages, images, and data. When you use Zoom’s web client, HTTP ensures that your browser retrieves Zoom’s interface and functionality.

↘️GET and POST

• GET – Used to request data from a server (e.g., opening a webpage).

• POST – Used to send data to a server (e.g., submitting a Zoom login form).

Versions of HTTP & Their Evolution

🔏What is HTTPS?

HTTPS (Hypertext Transfer Protocol Secure) is simply HTTP with encryption. It uses TLS (Transport Layer Security) to keep data safe while travelling across the internet, protecting sensitive information like passwords and financial details.

HTTP Status Codes (Common Responses from Servers)

When a browser makes an HTTP request, servers respond with status codes that indicate success or errors:

• 1xx (Informational) – The request is received, processing continues.

• 2xx (Success) – The request was successfully received and processed (e.g., 200 OK).

• 3xx (Redirection) – Further action is needed to complete the request (e.g., 301 Moved Permanently).

• 4xx (Client Errors) – The request is incorrect or unauthorized (e.g., 404 Not Found, 403 Forbidden).

• 5xx (Server Errors) – The server failed to fulfil the request (e.g., 500 Internal Server Error).

📌 2. DNS – The Internet’s Address Book

The Domain Name System (DNS) acts like the internet’s phonebook, translating human-friendly domain names (e.g., zoom.us) into numerical IP addresses (e.g., 192.168.1.1). Without DNS, we’d have to remember long sequences of numbers for every website we visit.

How DNS Resolution Works (Step-by-Step)

When you enter zoom.us in your browser, here’s what happens behind the scenes:

1. Browser Cache Check – The browser first checks if it has the IP address stored from a previous visit. If found, it skips the lookup. If not, the OS also checks its local DNS cache.

2. Query to Resolver – If the IP isn’t found, the request goes to a DNS resolver (usually provided by your ISP or public services like Google DNS 8.8.8.8 or Cloudflare DNS 1.1.1.1).

3. Root Server Contact – The DNS resolver queries a Root DNS Server, which directs it to the correct Top-Level Domain (TLD) Server (.com, .us, .org, etc.).

4. TLD Server Contact – The TLD server then points the request to the Authoritative DNS Server, which knows the exact IP address for zoom.us.

5. Retrieving the IP Address – The Authoritative DNS Server provides the correct IP address (170.114.52.2 for zoom.us).

6. Returning to the Browser – The DNS resolver sends the IP address back to your browser, which then establishes a connection to Zoom’s server to load the website or initiate a call.

Understanding DNS Components

💡 Analogy: Think of DNS like searching for a contact in your phone. Instead of memorizing numbers, you type a name, and your phone retrieves the number instantly, just like DNS fetches the correct IP address for websites.

---

📌 3. Understanding the OSI Model: The Backbone of Networking

The OSI (Open Systems Interconnection) Model is a conceptual framework that describes how data moves through a network. It consists of seven layers, each responsible for a specific function.

Let’s explore each layer and its function in network communication.

🎥 Zoom & The OSI Model: The Layers of a Video Call

The OSI (Open Systems Interconnection) model explains how data moves through a network in seven layers. Here’s how Zoom fits in:

1️⃣ Physical Layer – Hardware at Work

• Your microphone, webcam, and network cables send and receive physical signals.

  Example: Your Wi-Fi adapter transmits Zoom data wirelessly.

2️⃣ Data Link Layer – The Error Fixer

• Ensures data is transmitted correctly over Ethernet or Wi-Fi.

  Example: Your router checks and corrects any data transmission errors.

3️⃣ Network Layer – The Global Traffic Controller

• Uses IP addresses to route packets between you and Zoom’s servers.

  Example: When you join a meeting, your IP helps Zoom connect your device.

4️⃣ Transport Layer – Speed vs. Reliability

• UDP: Used for video/audio because it’s fast (even if some packets are lost).

• TCP: Used for chat and file transfers to ensure all packets arrive correctly.

5️⃣ Session Layer – Keeping Connections Alive

• Maintains stable connections for meetings and screen sharing.

  Example: Switching from video to screen share without disconnecting.

6️⃣ Presentation Layer – Making Data Usable

• Converts raw data into formats you can see and hear.

  Example: Zoom compresses video using H.264 codecs.

7️⃣ Application Layer – The Zoom Interface

• Everything you see: buttons, chat, video streams, and screen sharing.

  Example: Clicking “Join Meeting” interacts with Zoom’s application layer.

🛜 TCP vs UDP

Now that we’ve seen how data flows through the OSI model, let’s talk about the two main ways it actually gets delivered: TCP and UDP. Think of them as different traffic rules for your internet data!

💡 In Simple Terms:

• Use TCP when accuracy matters (e.g., web pages, file downloads).

• Use UDP when speed is more important than reliability (e.g., video calls, gaming).

📽️ Zoom uses TCP, UDP, and its own custom transport protocols to optimize real-time communication. It primarily relies on UDP for low-latency audio and video transmission but falls back to TCP when network conditions require more reliability. Additionally, Zoom implements proprietary transport mechanisms to enhance performance across varying network conditions.

📌 4. Making a Reliable & Secure Connection: The TCP & TLS Handshakes 🤝

Now that we've covered how data travels across networks using the OSI model, the role of HTTP for web communication, and how DNS resolves domain names into IP addresses, it's time to dive into the mechanisms that ensure our connection is both reliable and secure.

When you connect to Zoom (or any secure website), your device doesn’t just send data blindly—it first establishes a stable connection using the TCP handshake and then ensures encryption with the TLS handshake. These two processes work together to make sure that:
✔️ The connection is established without errors (reliability - TCP)
✔️ Data is encrypted and cannot be read by attackers (security - TLS)

Let's break them down! 🚀

1️⃣ TCP Handshake (For Reliability)

Before Zoom can securely encrypt your data, it first needs to set up a stable connection between your device and its servers. That’s where the TCP Handshake comes in.

Imagine trying to have a conversation over the phone—you need to confirm the other person can hear you before you start speaking. Similarly, TCP ensures that both your device and Zoom’s server are ready before exchanging data. This prevents delays, lost messages, or dropped connections during your video call. Let’s see how it works:

1. SYN (Synchronize) – Your device sends a request to Zoom’s server to establish a connection.

2. SYN-ACK (Synchronize-Acknowledge) – The server acknowledges the request and responds.

3. ACK (Acknowledge) – Your device confirms receipt, and the connection is established.

2️⃣ TLS Handshake (For Security)

1. Client Hello – The client (your device) sends a request to start a secure connection, listing supported encryption algorithms.

2. Server Hello – The server responds by selecting an encryption method from the client’s list.

3. Certificate – The server provides an SSL/TLS certificate to prove its identity, signed by a trusted authority.

4. Server Key Exchange (if needed) – For certain encryption methods (like Diffie-Hellman), the server shares additional key exchange data.

5. Certificate Request (optional) – The server may ask the client to provide its own certificate for authentication.

6. Client Certificate (if requested) – The client sends its certificate if required for mutual authentication.

7. Client Key Exchange – The client generates and sends a pre-master secret, which both sides will use to generate a shared encryption key.

8. ChangeCipherSpec – The client and server tell each other that all future communication will be encrypted using the agreed-upon key.

9. Finished – Both client and server send a final verification message to confirm encryption is working correctly.

Difference Between TCP Three-Way Handshake & TLS Handshake

🔹 Why is this important?

• The TLS handshake ensures security (encryption).

• The TCP handshake ensures reliability (successful connection).

  📌 Conclusion

Every time you start a Zoom call, multiple networking technologies work together behind the scenes. From DNS resolution to TLS security and packet transmission, Zoom leverages the internet’s architecture to deliver smooth, real-time communication.

While we’ve covered the basics of networking using Zoom as an example, many other technologies work together behind the scenes to make modern communication possible. 🚀

Next time you’re on a call, impress your friends by explaining the magic of networking that makes it all possible! 😎

---

🔗 References & Further Reading

For a deeper dive into the topics covered in this article, check out the following resources:

A huge thanks to the following resources and mentors who helped shape this article:

🔹 Special Thanks To:

• Piyush Garg and Hitesh Choudhary for their mentorship and guidance.

🔹 Informative Articles & Guides:

1. Chaicode – Video Lectures

2. GeeksforGeeks – How the Internet Works.

3. GeeksforGeeks – HTTP 3 and QUIC

4. Hostinger – What Is DNS: A Comprehensive Guide.

5. GeeksforGeeks – Understanding OSI Layers.

6. GeeksforGeeks – Designing Zoom - System Design.

7. GeeksforGeeks – TCP 3-Way Handshake.

8. Cloudflare – What happens in a TLS handshake?

9. SSL - SSL/TLS Handshake: Ensuring Secure Online Interactions

🔹 Tools Used:

1. Figma – Used for designing diagrams and illustrations.

2. Chatgpt – Used for document structure and content improvement.

---

🚀 Enjoyed this? Share it with your friends and simplify networking together!